Coffee Appreciation

I used to have a similar machine, if I remember rightly the pressurised gubbins is to produce more crema but it's 'false' crema. I do remember seeing guide to modding the machine, do a google search, someone will have asked this question on a coffee site before! I don't think it's just as easy as changing the portafilter though I could be wrong!

I have a portafilter question. (Please forgive/correct any misuse of the terminology as I am relatively new to making espresso at home). I have a DeLonghi Icona espresso machine with a pressurised portafilter. Is it possible to get a replacement basket for this machine so it's not pressurised? If so, how do I know what the important dimensions are?

Thanks.